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Polymers
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Green Polymer Composites for Circular Economy
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Green Polymer Composites for Circular Economy

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Circular and Green Polymer Science".

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 2475

Special Issue Editor

Dr. Marwa Tallawi

E-Mail Website
Guest Editor
Chair of Carbon Composites, TUM School of Engineering and Design, Technical University of Munich, 85354 Freising, Germany
Interests: hydrogel; biopolymers; sustainable polymers; biomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Growing environmental concern has led to traditional thermoplastics’ and thermosets’ use as matrices for composite fabrication. However, criticism of their poor decomposition and recyclability has arisen. The disposal of these composites has a significant impact on the environment. Petroleum-based plastic composites have superior properties; however, they are associated with a significant CO2 fingerprint, as they are usually incinerated at the end of their life cycle, releasing large amounts of CO2, or are discarded into landfills or seas, where they accumulate exponentially for decades. The increased use of composite materials has led to a massive amount of waste being generated, which primarily consists of scraps and end-of-life components. Today, composite waste is shredded, burned, or landfilled. Composites indeed have superior properties, such as lightweight structures and high performance. However, the treatment of composite waste presents a significant challenge due to pollution concerns and new legal standards. Recycling these materials comes with negative economic and environmental impacts. The development of polymers using natural and biogenic building monomers, however, promises more sustainable environment and facile recycling processes. Sustainable polymers, which have the potential to alleviate some of the long-term pollution problems caused by conventional plastic composites, have become a research focus worldwide, with new commercial products and applications continuously emerging for these green composites. Green composites are regarded as the next generation of sustainable composite materials. This Special Issue aims to present the latest advances in green composite development, fabrication, characterization and application

Dr. Marwa Tallawi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • green composites
  • biobased
  • thermoset
  • high performance
  • facile recycling

Published Papers (3 papers)

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Research

17 pages, 6930 KiB  
Article
Strategies towards Fully Recyclable Commercial Epoxy Resins: Diels–Alder Structures in Sustainable Composites
by Julio Vidal, Carlos Hornero, Silvia De la Flor, Anna Vilanova, Jose Antonio Dieste and Pere Castell
Polymers 2024, 16(8), 1024; https://doi.org/10.3390/polym16081024 - 09 Apr 2024
Viewed by 448
Abstract
The Diels–Alder equilibrium is a widely known process in chemistry that can be used to provide a thermoset structure with recyclability and reprocessability mechanisms. In this study, a commercial epoxy resin is modified through the integration of functional groups into the network structure [...] Read more.
The Diels–Alder equilibrium is a widely known process in chemistry that can be used to provide a thermoset structure with recyclability and reprocessability mechanisms. In this study, a commercial epoxy resin is modified through the integration of functional groups into the network structure to provide superior performance. The present study has demonstrated that it is possible to adapt the curing process to efficiently incorporate these moieties in the final structure of commercial epoxy-based resins. It also evaluates the impact that they have on the final properties of the cured composites. In addition, different approaches have been studied for the incorporation of the functional group, adjusting and adapting the stoichiometry of the system components due to the differences in reactivity caused by the presence of the incorporated reactive groups, with the objective of maintaining comparable ratios of epoxy/amine groups in the formulation. Finally, it has been demonstrated that although the Diels–Alder equilibrium responds under external conditions, such as temperature, different sets of parameters and behaviors are to be expected as the structures are integrated into the thermoset, generating new equilibrium temperatures. In this way, the present research has explored sustainable strategies to enable the recyclability of commercial thermoset systems through crosslinking control and its modification. Full article
(This article belongs to the Special Issue Green Polymer Composites for Circular Economy)
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14 pages, 3719 KiB  
Article
Circular Economy Insights on the Suitability of New Tri-Layer Compostable Packaging Films after Degradation in Storage Conditions
by Ricardo Ballestar de las Heras, Sergio Fernández Ayala, Estefanía Molina Salazar, Fernando Carrillo, Javier Cañavate and Xavier Colom
Polymers 2023, 15(20), 4154; https://doi.org/10.3390/polym15204154 - 19 Oct 2023
Cited by 2 | Viewed by 702
Abstract
The environmental degradation of the films used in packaging is a key factor in their commercial use. Industrial and academic research is aimed at obtaining materials that have degradation features that ensure their eco-sustainability but, at the same time, preserve their use properties [...] Read more.
The environmental degradation of the films used in packaging is a key factor in their commercial use. Industrial and academic research is aimed at obtaining materials that have degradation features that ensure their eco-sustainability but, at the same time, preserve their use properties during storage and distribution periods. This study analyzes the degradability behavior over time of commercial packaging that meets the requirements of the UNE 13432 standard and the prEN 17427 (2020) home composting certification requirements under standard storage conditions. The study attempts to provide insight into the durability of the films under standard storage conditions, verifying that this type of packaging has a useful life of more than 12 months and that after this storage period it still retains the usability properties for which it was conceived. The analyzed sample has been manufactured using a three-layer technology under some commercial formulations based on PBAT + STARCH + PLA and has been analyzed monthly for 12 consecutive months. The macroscopic monitoring of the degradation of the sample has been carried out through the evolution of the mechanical properties and the quantification of the color changes (very important in films) via colorimetry. The nature of the observed variations has been justified at the microstructural level from the data obtained in calorimetric analysis (DSC) and from the characterization using FTIR. The results indicate a loss of properties in the tensile, elongation and impact tests and a behavior of stability or improvement in the tear properties of the film. Analyzing the microstructural changes, it is observed that the degradation of a hydrolytic and thermo-oxidative type occurs in the amorphous part of the film. The conclusion of this study is that the proposed packaging, focused on domestic composting and stored under standard conditions, has a useful life of more than 12 months. This period should be sufficient to cover the stages of production, storage and final use. Full article
(This article belongs to the Special Issue Green Polymer Composites for Circular Economy)
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14 pages, 4428 KiB  
Article
Characterization and Application in Natural Rubber of Leucaena Leaf and Its Extracted Products
by Pattamaporn Klongklaew, Phimthong Khamjapo, Pongdhorn Sae-Oui, Pairote Jittham, Surapich Loykulnant and Weenusarin Intiya
Polymers 2023, 15(18), 3698; https://doi.org/10.3390/polym15183698 - 08 Sep 2023
Cited by 1 | Viewed by 890
Abstract
Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted [...] Read more.
Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted products on the cure characteristics and mechanical properties of natural rubber were investigated. The extraction of Leucaena leaf was carried out by using a proteolytic enzyme at 60 °C. The digested protein was separated from the residue by centrifugation. Both digested protein and residue were then dried and ground into powder, namely digested protein powder and residual powder, respectively, before being characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction, particle size determination, and protein analysis. After being added to natural rubber at 3 parts per hundred rubber, they significantly reduced both the scorch time and the optimum cure time of the rubber compounds, probably due to the presence of nitrogen-containing substances, without a significant sacrifice of the mechanical properties. For instance, the optimum cure time decreased by approximately 25.5, 35.4, and 54.9% for Leucaena leaf powder, residual powder, and digested protein powder, respectively. Thus, they can be used as green and sustainable fillers with a cure-activation effect in rubber compounding. Full article
(This article belongs to the Special Issue Green Polymer Composites for Circular Economy)
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